This invention relates to flexible containers of the flexitank type and has particular reference to flexible containers for potable liquids such as wine.
Flexitank type containers are used for the bulk transport of liquids. The containers conventionally comprise a fabric reinforced rubber body formed into a large pillow-like shape. The flexitank may be transported in a standard ISO container or may be transported on a flat pallet. The fabric reinforcement is relatively inextensible and provides the strength required to restrain the surging liquids in the container. The rubber prevents escape of liquid from the container.
In many cases the materials being transported are hydrocarbons or vegetable oils but recently it has been proposed to use flexitanks for the bulk transport of potable liquids, particularly wine. It will be appreciated that it is essential that the wine transported in such a flexible container should not become contaminated either by bacteria or by chemical compounds in the rubber tank material. Hitherto linered tanks have been provided principally to prevent the escape of liquid such as hydrocarbons from the tank. There are some passing references to the prevention of contamination of liquids in flexible containers but these have not, in the main, been put into practical operation.
Thus in British Patent Specification No. 988,807 there is described a flexible container provided with a liner of a barrier material to prevent contamination of foodstuff products. The external layer proposed is neoprene and the inner layer is normally a thermoweldable film such as polyvinyl chloride, polyethylene or a polyamide. Materials such as polythene and Teflon (a polytetrafluoroethylene) have to be stuck to a natural or synthetic rubber latex which can then be adhered to the external layer by pressure sensitive adhesive.
In British Patent Specification No. 983,240 there is described a flexible tank which is particularly intended for use in the transport of hydrocarbons. The principal objective is to prevent the diffusion of a thin stream of hydrocarbons escaping from the tank with a consequent risk of fire or explosion during long-term storage. The solution proposed is to use an internal film of a polyamide having a thickness of approximately 40 microns on the inside of the tank.
In British Patent Specification No. 805,106 there is described the use of polyethylene as a linear material, which polyethylene is vulcanised to an unreinforced butyl rubber layer. The combined composite of polyethylene and butyl rubber is then formed into a shape by stretching and afterwards an external rubberised fabric cover is provided which is bonded to the vulcanised rubber layer.
As far as is known such devices are not practically usable for the transport of potable liquids, particularly wine which is subject to a bacteria attack. It is found that when transporting wine in prior art type containers contamination of subsequent loads of wine can occur after the first load has been shipped and emptied. It will be appreciated that the flexible tank is normally used to transport wine from one country to another or for the transport of wine for large distances in one country, and after transporting one load the flexible tank will be cleaned, rolled up and re-used again, either later in the same season or in the following year. It has been found that wine transported subsequently in once-used tanks can become contaminated in the absence of the provisions of the present invention.